Click the thumbwheel from Comfort to Sport, and the Porsche will instantly flex its muscles. Twist it one notch further to Sport Plus, and the car mentally prepares itself for an excursion to the race track. Your best bet is thus Individual, which can blend compliant dampers with a fast shifter and an eager throttle response. Better still, dial in PSM Sport which is, on cold tyres, almost as exciting as PSM Off. If testing boundaries is all about putting abilities and ambitions into perspective, then the 718 is a better tool for the job. It is simply the more tactile car, provides feedback in abundance, talks you through the tricky bits with subtle body language, leaves some latitude before stepping in.
The Cayman is happy to indulge in the complete handling spectrum from mild understeer to wild oversteer. It is a classic case of challenge followed by instant reward, or instant punishment.
Having said that, the Audi is the quicker A to B car on certain days. Its trick driveline now boasts wheel-selective torque delivery, the cornering grip of the 2oin Pirelli P Zeros (the Cayman runs the same tyre) is little short of phenomenal, and in Dynamic mode more grunt can be relayed to the rear wheels in the blink of an eye. Through fast sweepers, the TT RS is surreally fast, poised and grounded. Where ripples and grooves start to annoy the Porsche, its challenger continues to be an unreservedly focused, unswerving carver. Even though the 718 has the four-piston front brakes of the 911, it cannot quite match the fast-rewind stopping power of a TT RS with carbon-ceramic rotors. Another forte of the coupe with the four rings is the sprint against the stopwatch. Thanks to quattro, launch control and an extra 44lb ft, red beats yellow by 3.7 against 4.2sec – that’s AMG GT-S and M6 territory.
At the end of the day, it’s the handling balance which costs the Audi precious points. Turn-in just isn’t quite as eager, because eventual understeer is the name of ten-tenths cornering exercises, and because the car likes to be in control. When we entered the zig-zag rollercoaster part of the route, the TT RS started with a tyre pressure of 2.3bar all-round. About 40 minutes later, rubber melting and brakes fuming, the readout signalled a jump to 3.3 up front and 2,6in the back. Sure, we could have let air out and hoped for the best on the re-run. Alternatively though, Audi could have agreed on a more adventurous torque split, not unlike the set-up Ford chose for the remarkable Focus RS. After all, truly fast cornering is not about overt lariness but about a predominantly neutral attitude that stretches a bit either way when required.
On paper, these two contenders have a lot in common. On the road, however, they display quite different strengths and weaknesses. The TT RS wears a flash and aggressive outfit, but it delivers when pushed, and its dynamic potential is remarkably accessible. The 718 Cayman S is a more complete car than last year’s GTS, and it ticks all the critical boxes, moving one more step closer to the iconic 911. Despite the paradigm shift towards the turbocharged flat-four, it still is the more emotional choice, the more engaging drive and the sole proper sports car.